1. Field of the Invention
The present invention relates to a zoom lens, or a zoom lens barrel, and more specifically to a movable lens hood mechanism of the zoom lens.
2. Description of the Related Art
In a zoom lens whose angle of view varies in accordance with a variation of the focal length, unwanted light is preferably prevented from being incident on the lens surface in accordance with a variation of the angle of view. However, a zoom lens having a lens hood which can vary the maximum incident angle of light to the lens surface in accordance with a variation of the angle of view is not known in the art.
The present invention has been devised in view of the above-described problem, wherein an object of the present invention is to provide a zoom lens having a movable lens hood which can vary the maximum incident angle of light to the lens surface in accordance with a variation of the angle of view.
To achieve the object mentioned above, according to an aspect of the present invention, a movable lens hood mechanism of a zoom lens is provided, including a plurality of lens groups guided linearly in a direction of an optical axis to change a focal length of the zoom lens; a first cam barrel driven to rotate to move the plurality of lens groups in the optical axis direction; a movable hood barrel having a photographic aperture positioned in front of the frontmost lens group of the plurality of lens groups and guided linearly in the optical axis direction; and a feed mechanism which drives the movable hood barrel forward and rearward in the optical axis direction relative to the frontmost lens group by rotation of the first cam barrel so that a space between the photographic aperture of the movable lens hood and the frontmost lens group in the optical axis direction varies in accordance with a variation of a focal length of the zoom lens.
Preferably, the feed mechanism includes a second cam barrel for driving the moveable hood barrel forward and rearward in the optical axis direction, wherein the first cam barrel and second cam barrel are provided separately from each other, and the first cam barrel and second cam barrel rotate together about the optical axis.
Preferably, a barrier block is further provided fixed to a front end of the movable hood barrel to open and close the photographic aperture of the zoom lens.
In an embodiment, the feed mechanism includes a second cam barrel for driving the moveable hood barrel forward and rearward in the optical axis direction, wherein the first cam barrel and second cam barrel are provided separately from each other, and the first cam barrel and second cam barrel rotate together about the optical axis. The barrier block includes at least one barrier blade driven to open and close the photographic aperture, the movable lens hood mechanism further including a barrier drive ring driven to rotate by rotation of the second cam barrel to open and close the at least one barrier blade.
The above-described zoom lens can be incorporated in a digital camera.
In an embodiment, the feed mechanism includes a second cam barrel which is fitted on the first cam barrel, wherein the movable hood barrel is driven forward and rearward in the optical axis direction by rotation of the first cam barrel via the second cam barrel of the feed mechanism.
In an embodiment, the feed mechanism further includes a plurality of inward pins, fixed to the moveable hood barrel, which project radially inwards; and a corresponding plurality of guide grooves formed on an outer peripheral surface of the second cam barrel, the plurality of inward pins being respectively engaged in the corresponding plurality of guide grooves so that the moveable hood barrel moves in the optical axis direction by rotation of the second cam barrel.
According to another aspect of the present invention, a movable lens hood mechanism of a zoom lens is provided, including a movable lens hood guided along an optical axis; and a feed mechanism which drives the movable lens hood forward and rearward along the optical axis to vary a maximum incident angle of light to a front surface of a frontmost lens group of the zoom lens in accordance with a variation of the angle of view of the zoom lens.
Preferably, a barrier block is provided fixed to the front end of the movable lens hood and having at least one barrier blade for opening and closing a photographic aperture of the zoom lens.
In an embodiment, the movable lens hood mechanism further includes a rotation transfer recess formed on an outer peripheral surface of the second cam barrel, and a driven lever provided on the movable hood barrel. When a relative distance in the optical axis direction between the second cam barrel and the movable hood barrel becomes less than a predetermined distance, the driven lever associates with the rotation transfer recess so that the rotation of the second cam barrel is transmitted to the driven lever.
According to another aspect of the present invention, a zoom lens is provided, including a plurality of lens groups which are moved with respect to each other to change a focal length of the zoom lens; a focusing lens group positioned behind the plurality of lens groups and driven in a direction of the optical axis to bring an object to be photographed into focus; a first cam barrel having at least one cam groove on an inner peripheral surface of the first cam barrel, at least one of the plurality of lens groups being moved in the optical axis direction by rotation of the first cam barrel in accordance with a profile of the at least one cam groove; a second cam barrel which is fitted on a front part of an outer peripheral surface of the first cam barrel to be rotatable about the optical axis together with the first cam barrel; a movable hood barrel positioned around the second cam barrel and guided in the optical axis direction; at least one inward pin fixed to the movable hood barrel to project radially inwards; and at least one guide groove formed on an outer peripheral surface of the second cam barrel, the at least one inward pin being respectively engaged in the at least one guide groove so that the movable hood barrel is driven forward and rearward in the optical axis direction relative to a frontmost lens group of the plurality of lens groups by rotation of the second cam barrel.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2000-24040 (filed on Feb. 1, 2000) which is expressly incorporated herein by reference in its entirety.